Filed under: Geoengineering, Interventions in the carbon/climate crisis
There’s a letter to the editor in this week’s Nature from Jim Lovelock and Chris Rapley (late of the BAS, now at the Natural History Museum) suggesting that pumping up nutrient rich water from below the mixed surface surface layer of the oceans would increase the rate of photosynthesis in the seas above and thus pull down carbon from the atmosphere. Key para:
The oceans, which cover more than 70% of the Earth’s surface, are a promising place to seek a regulating influence. One approach would be to use free-floating or tethered vertical pipes to increase the mixing of nutrient-rich waters below the thermocline with the relatively barren waters at the ocean surface. (We acknowledge advice from Armand Neukermans on engineering aspects of the pipes.) Water pumped up pipes — say, 100 to 200 metres long, 10 metres in diameter and with a one-way flap valve at the lower end for pumping by wave movement — would fertilize algae in the surface waters and encourage them to bloom. This would pump down carbon dioxide and produce dimethyl sulphide, the precursor of nuclei that form sunlight-reflecting clouds.
There will be a lot of people who don’t like this suggestion for a lot of reasons (I wrote about some of the generalised disapproval of “geoengineering” in a Nature feature a few months back, and see also these blog posts (first | second) over at Climate Feedback). As well as the generalised mistrust of engineering interventions, though, I suspect that there will be some pretty specific criticisms, as my colleague Quirin Schiermeier notes in a news@nature article on the subject. Here’s his take on the downside:
“The concept is flawed,” says Scott Doney, a marine chemist at WHOI. He says it neglects the fact that deeper waters with high nutrients also generally contain a lot of dissolved inorganic carbon, including dissolved CO2. Bringing these waters to the lower pressures of the surface would result in the CO2 bubbling out into the air. So contrary to the desired effect, the scheme could result in a net ‘outgassing’ of CO2, he warns. “There is no technological fix for this problem,” he says.
Others say such a project would have no net effect on CO2 in the atmosphere. “At every meeting I’ve been to, when they have talked about this idea for surface ocean CO2 removal, the point has been made that you would bring up nutrients and inorganic carbon in the same ratio as you remove as biomass,” says Ken Buesseler, a marine chemist at WHOI. And there are potentially many harmful impacts on sea life, he says.
I haven’t taken on board the wider press coverage, but I hear that various oceanographers — including some who are not ideologically averse to a touch of geoengineering — share these or similar doubts. One encouraging thing is to learn from Quirin that David Karl (author of a fine review that touches on some of the science behind all this in the Nature Reviews Microbiology oceans special I was enthusing about earlier) will soon be trying out a pump along these lines made by Atmocean and seeing what effects it has. That experiment will surely teach us something, just as the iron fertilization experiments being discussed at Woods Hole this week have. And just as in the iron case, there should be exciting science on how the oceans work here even if there’s no world-saving breakthrough.
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